Blends of thermoplastic copolyester elastomers with vinyl chloride polymers

ABSTRACT

A uniform blend of about 5-95% by weight vinyl chloride polymer having a tensile modulus of at least about 50,000 p.s.i. and about 95-5% by weight of at least one thermoplastic segmented copolyester .[.polymer.]. containing (1) about 5-90 weight percent long chain ester units derived from at least one long chain glycol having a molecular weight of about 600-6000 and at least one low molecular weight dicarboxylic acid having a molecular weight less than about 300, and (2) about 10-95 weight percent short chain ester units derived from at least one low molecular weight diol having a molecular weight of less than about 250 and at least one low molecular weight dicarboxylic acid having a molecular weight of less than about 300. These blends exhibit excellent abrasion resistance which is maintained even in the presence of a large amount of plasticizer, improved low temperature flexibility, impact resistance and increased scuff resistance. These blends also exhibit improved processing because of excellent thermal stability and low melt viscosity.

BACKGROUND OF THE INVENTION

Thermoplastic polymers of vinyl chloride are used for a variety ofpurposes such as pipes, tubing, hose, sheet, shoe soles, coated fabrics,wire covering, flooring, and weatherstripping. Because suchthermoplastic polymers are generally brittle and exhibit poor elongationand abrasion properties, it has been common practice to add variousmodifiers such as thermoplastic polyurethanes, monomeric plasticizers,low molecular weight aliphatic polyesters, and nitrile rubber; however,blends containing such modifiers suffer a variety of disadvantages suchas volatility, hydrolytic instability, poor abrasion resistance,susceptibility to fungus, processing difficulties, and poor lowtemperature properties. There has been a need for a modifier forthermoplastic polymers of vinyl chloride which imparts good abrasionresistance, impact resistance, fungus resistance, improvedprocessability, good low temperature properties and improved hydrolyticstability to such modified compositions.

SUMMARY OF THE INVENTION

According to this invention there is provided a uniform blend of about5-95% by weight vinyl chloride polymer (the term polymer includes vinylchloride copolymer) having a tensile modulus of at least about 50,000p.s.i. by ASTM D-638, and about 95-5% by weight of at least onethermoplastic segmented copolyester .[.polymer.]. comprising (1) 5-90weight percent long chain ester units or segments derived from at leastone long chain glycol having a molecular weight of about 600-6000 and atleast one low molecular weight dicarboxylic acid having a molecularweight less than about 300, and (2) 10-95 weight percent short chainester units derived from at least one low molecular weight diol having amolecular weight of less than about 250 and at least one low molecularweight dicarboxylic acid having a molecular weight of less than about300.

The blends prepared in accordance with this invention are fungusresistant, exhibit a wide processing temperature range, have good lowtemperature properties, are nonvolatile, have good impact resistance,have exceptionally high abrasion resistance which is maintained even inthe presence of large amounts of plasticizers or filler, and haveimproved hydrolytic stability. In addition blends which are rich in thecopolyester .[.polymer.]. exhibit improved stiffness, scuff resistanceand in many instances, improved tear strength. Relative to polymericplasticizers such as thermoplastic urethanes, the copolyesters of thisinvention are more thermally stable, permitting a wider range ofprocessing temperatures, do not stick to highly polished chrome-platedprocessing rolls, and permit use of higher shear (more efficient) mixingscrews.

DETAILED DESCRIPTION

Generally the copolyesters useful in this invention are segmentedcopolyester polymers consisting essentially of recurring intralinearlong chain ester units and short chain ester units randomly joinedhead-to-tail through ester linkages, said long chain ester units beingrepresented by the formula ##EQU1## and said short chain ester unitsbeing represented by the formula ##EQU2## where G is a divalent radicalremaining after the removal of terminal hydroxyl groups from at leastone long chain glycol having a molecular weight of about 600-6000; R isa divalent radical remaining after removal of carboxyl groups from atleast one dicarboxylic acid having a molecular weight less than about300; and D is a divalent radical remaining after removal of hydroxylgroups from at least one low molecular weight diol having a molecularweight less than 250.

Copolyesters of the type described herein which have high melting pointsdo not blend readily with polymers of vinyl chloride at safe processingtemperatures for vinyl chloride polymers. Therefore copolyesters havingmelting points in excess of 215° C. are not preferred for use in thecompositions of the present invention unless they are first pre-mixedwith plasticizers so that mixing temperatures are reduced to anacceptable level for vinyl incorporation.

Segmented copolyester polymers useful for compositions of this inventionare generally (guidelines for preparing polymers having desirably lowmelting points are given hereinafter) produced by reacting together in amixture at least one long chain glycol, at least one low molecularweight diol, and at least one dicarboxylic acid. The long chain esterunits are segments of the copolyester chain which are the reactionproduct of the long chain glycol and the dicarboxylic acid. The shortchain ester units are segments of the copolyester chain which are thereaction product of the low molecular weight diol and the dicarboxylicacid. The reaction is conducted by conventional methods and conditions.The short chain ester units should be chosen so that a polymer made upsolely of short chain ester units and having a molecular weight in thefiber-forming range (>5000), has a melting point of at least 150° C. Themelting point is determined by extinction of polarized light observedwhile the sample is heated on a hot stage microscope substantially bythe procedure described in "Preparative Methods of Polymer Chemistry,"Sorenson and Campbell, Interscience Publishers, second edition, 1968,pages 53-55. The melting point is the average of the temperatures atwhich the first and last sample particles blend with the backgroundwhile heating at 1° C./minute after first annealing the sample for 30minutes at a temperature about 20° C. below the approximate meltingpoint.

Generally, the long chain and the short chain units combine to form thecopolyester .[.polymer.]. according to their tendencies to react underthe conditions used. This order of combination can be termed random orstatistical. The various ester units are combined in a head-to-tailarrangement through ester linkages forming a substantially interlinearpolymer. The exact polymer chain configuration is not critical as longas the various reactant and proportion parameters are met.

Copolyester polymers which are particularly useful for compositions ofthis invention have 5-90 weight percent long chain ester units and atleast 50 mole percent of the total short chain ester units of the sametype, i.e., derived from one type of acid and one type of low molecularweight diol. Copolyesters having 30-65 weight percent long chain esterunits are preferred. Such preferred copolyesters are described in U.S.Pat. 3,023,192 to Shivers.

Copolyester polymers useful for making the compositions of thisinvention can be conveniently made by conventional ester interchangereaction. A preferred procedure involves heating at about 150-260° C.the dimethyl ester of a dicarboxylic acid with a long chain glycol and amolar excess of a short chain diol in the presence of an esterinterchange catalyst. Methanol formed by the interchange reaction isdistilled off and heating is continued until methanol evolution iscompleted. The interchange reaction or polymerization is typicallycomplete within a few minutes to a few hours depending upon theparticular temperature, catalyst, glycol excess, and reactants used.This procedure produces a low molecular weight prepolymer which can betransformed into high molecular weight copolyester by additional esterinterchange as described herein.

Low molecular weight prepolymer can be prepared by other esterinterchange procedures. A long chain glycol can be reacted with a highor low molecular weight short chain ester homopolymer or copolymer inthe presence of ester interchange catalyst until a random esterprepolymer is produced by the interchange reactions. Short chain esterhomopolymer or copolymer can be prepared by ester interchange fromeither dimethyl esters and low molecular weight diols, as above, or fromfree acids with diol acetates. Short chain ester copolymer can beprepared by direct esterification of appropriate acids, anhydrides, oracid chlorides with diols or alternatively by reaction of the acids withcyclic ethers or carbonates. Ester prepolymer can also be prepared byusing a long chain glycol in place of a diol or using a mixture ofreactants.

Molecular weight of the ester prepolymer is increased by removing excessshort chain diol by distilling it from the prepolymer. This operation isfrequently referred to as "polycondensation." Additional esterinterchange occurs during the distillation to increase the molecularweight and to further randomize the arrangement of the copolyesterunits. The distillation conditions typically are less than 5 mm. Hg, at220-280° C. Antioxidants, such assym-di-beta-naphthyl-p-phenylenediamine and 1,3,5-trimethyl - 2,4,6 -tris(3,5 - ditertiary-butyl-4-hydroxybenzyl)benzene can be added toreduce degradation.

To increase the rate of ester interchange catalysts can be employed forthe prepolymer and polycondensation steps. Any one of a wide variety ofwell-known catalysts can be used, but organic titanates, such astetrabutyl titanate either alone or combined with magnesium or zincacetates, are preferred. Complex titanates derived from alkali oralkaline earth metal alkoxides and titanate esters are very effective.Inorganic titanates (such as lanthanum titanate), calciumacetate/antimony trioxide mixtures, and lithium and magnesium alkoxidesare other catalysts which can be used. The polycondensation can also beaccelerated by adding diaryl esters or carbonates as disclosed in U.S.Pat. 3,433,770 and 3,444,141, respectively, both to Teijin Limited.

Ester interchange polymerizations are generally run in a melt withoutadded solvent, but inert solvent can be used to facilitate removal ofvolatile components from the mass at low temperatures. Other specialprocessing techniques, such as azeotropic distillation using a solventto prepare prepolymer and interfacial polymerization, can be used forspecific polymers and problems. Both batch and continuous methods can beused for any stage of copolyester polymer preparation. Polycondensation.[.of prepolymer.]. can also be accomplished in the solid phase byheating finely divided solid prepolymer in a vacuum or in a stream ofinert gas to remove liberated low molecular weight diol. This method hasthe advantage of reducing degradation because it must be used attemperatures below the softening point of the prepolymer. The majordisadvantage is the long time required to reach a given degree ofpolymerization.

Long chain glycols which can be used to produce the copolyester polymersuseful for the compositions of this invention are substantially linearglycols having hydroxyl groups on the chain which are terminal, or asnearly terminal as possible, and having a molecular weight of aboveabout 600 and preferably 600-6000.

A preferred group of long chain glycols have a melting point of lessthan about 60° C. and a carbon to oxygen ratio of at least about 2.These preferred glycols produce compositions having elastomericcharacter.

Long chain glycols which can be used to prepare copolyester polymersuseful for the composition of this invention include poly(alkyleneoxide)glycols wherein the alkylene group has 2-10 carbon atoms, such as

poly(ethylene oxide)glycol,

poly (1,2- and 1,3-propylene oxide)glycol,

poly(tetramethylene oxide)glycol,

poly(pentamethylene oxide)glycol,

poly(hexamethylene oxide)glycol,

poly(heptamethylene oxide)glycol,

poly(octamethylene oxide)glycol,

poly(nonamethylene oxide)glycol, and

poly (1,2-butylene oxide)glycol;

random or block copolymers of ethylene oxide and 1,2-propylene oxide,and poly-formals prepared by reacting formaldehyde with glycols, such aspropylene glycol, or mixtures of glycols, such as a mixture oftetramethylene and pentametylene glycols.

Long chain glycols can also be formed in situ from dicarboxymethyl acidsof poly(alkylene oxides) such as ##EQU3## derived frompolytetramethylene oxide. When the long chain dicarboxylic acids (IIIabove) are added to the polymerization mixture as acids, they react withthe low molecular weight diol or diols present in excess to form thecorresponding poly(alkylene oxide)ester glycols. The dicarboxylic acidscan also react with long chain glycols which are present, in which casediol units (D) in the polymer chain are polymeric residues of the longchain glycols. However, this second reaction occurs only to a verylimited degree because the low molecular weight diol is present inconsiderable molar excess.

Polythioether glycols and polyester glycols can also be used as theglycols for producing copolyester polymers for the compositions of thisinvention. With polyester glycols care must generally be exercised toreduce tendency of such glycols to interchange during polymerization.Either polybutadiene or polyisoprene glycols, copolymers of these, andsaturated hydrogenation products of these materials can be used as longchain glycols herein. Glycol esters of dicarboxylic acids formed byoxidation of polyisobutylene diene copolymers can also be used asglycols for the copolyester polymers useful for compositions of thisinvention.

Poly(tetramethylene oxide)glycol, poly(1,2-propylene oxide)glycol,poly(ethylene oxide)glycol and poly(1,2-propylene oxide)glycol cappedwith ethylene oxide units are preferred long chain glycols.

Dicarboxylic acids which can be used to produce the copolyester.[.polymer.]. useful for compositions of this invention are aliphatic,cycloaliphatic, or aromatic dicarboxylic acids of a low molecularweight, i.e., having a molecular weight of less than about 300.Dicarboxylic acids, as used herein, include acid equivalents having twofunctional carboxyl groups which perform substantially like dicarboxylicacids in reaction with glycols and diols forming copolyester polymers.These equivalents include esters, ester-forming derivatives, such asacid halides and anhydrides, and other derivatives which behavesubstantially like dicarboxylic acids forming esters with glycols anddiols. The molecular weight requirement pertains to the acid and not toits equivalent, ester or ester-forming derivative. Thus, an ester of adicarboxylic acid having a molecular weight greater than 300 or an acidequivalent of a dicarboxylic acid having a molecular weight greater than300 are included provided the acid has a molecular weight below about300. The dicarboxylic acids can contain any substituent groups orcombinations which do not substantially interfere with the copolyesterpolymer formation and use of the polymer in the thermoplasticcompositions of this invention.

Aliphatic dicarboxylic acids, as the term is used herein, refers tocarboxylic acids having two carboxyl groups each attached to a saturatedcarbon atom. If the carbon atom to which the carboxyl group is attachedis saturated and is in a ring, the acid is cycloaliphatic. Aliphatic orcycloaliphatic acids having conjugated unsaturation cannot be usedbecause such acids do not satisfactorily form the copolyester polymersnecessary for the compositions of this invention, but acids havingunsaturation which is not conjugated can be used.

Aromatic dicarboxylic acids, as the term is used herein, aredicarboxylic acids having two carboxyl groups attached to a carbon atomin an isolated or fused benzene ring. It is not necessary that bothfunctional carboxyl groups be attached to the same aromatic ring andwhere more than one ring is present, they can be joined by aliphatic oraromatic divalent radicals or divalent radicals such as --O-- or --SO₂--.

Representative aliphatic and cycloaliphatic acids which can be used forthis invention are sebacic acid, 1,3-cyclohexane dicarboxylic acid,1,4-cyclohexane dicarboxylic acid, adipic acid, glutaric acid, succinicacid, carbonic acid, oxalic acid, azelaic acid, diethylmalonic acid,allylmalonic acid, 4-cyclohexene-1,2-dicarboxylic acid, 2-ethylsubericacid, 2,2,3,3-tetramethylsuccinic acid, cyclopentanedicarboxylic acid,decahydro-1,5-naphthylene dicarboxylic acid, 4,4'-bicyclohexyldicarboxylic acid, decahydro-2,6-naphthylene dicarboxylic acid,4,4'-methylene-bis(cyclohexyl carboxylic acid), 3,4-furan dicarboxylicacid, and 1,1-cyclobutane dicarboxylic acid. Preferred can be used forthis invention are sebacic acid, 1,3-cycloaliphatic acids arecyclohexanedicarboxylic acids and adipic acid.

Representative aromatic dicarboxylic acids which can be used includephthalic, terephthalic, and isophthalic acids, bibenzoic acid,substituted dicarboxy compounds with two benzene nuclei such asbis(p-carboxyphenyl) methane, p-oxy(p-carboxyphenyl) benzoic acid,ethylene-bis(p-oxybenzoic acid), 1,5-naphthalene dicarboxylic acid,2,6-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid,phenanthralene dicarboxylic acid, anthralene dicarboxylic acid,4,4'-sulfonyl dibenzoic acid, C₁ -C₁₂ alkyl and ring substitutionderivatives thereof, such as halo, alkoxy, and aryl derivatives.Hydroxyl acids such as p(beta-hydroxyethoxy) benzoic acid can also beused providing an aromatic dicarboxylic acid is also present.

Aromatic dicarboxylic acids are a preferred class for preparing thecopolyester polymers useful for compositions of this invention becausethese elastomeric polymers inherently have good hydrolytic stability.Among these aromatic acids those with 8-16 carbon atoms are preferred,particularly the phenylene dicarboxylic acids, i.e., phthalic,terephthalic, and isophthalic acids.

Low molecular weight diols which can be used to produce copolyesterpolymers useful in the compositions of this invention are aliphatic,cycloaliphatic, and aromatic diols having a molecular weight of lessthan about 250 and two functional hydroxyl groups. Diol equivalentswhich form esters with dicarboxylic acids are included and the molecularweight requirement applies only to the diol and not to its equivalent.Such equivalents are illustrated by ethylene oxide and ethylenecarbonate which can be used in the place of ethylene glycol.

The terms "aliphatic," "cycloaliphatic," and "aromatic" as used todefine the diols useful for this invention have the same general meaningas applied to the dicarboxylic acids and glycols set forth herein withthe location of the functional hydroxyl groups being the determiningfactor similar to the location of the carboxyl groups for thedicarboxylic acids.

Preferred low molecular weight diols useful for preparing compositionsof this invention include diols having 2-15 carbon atoms such asethylene, 1,2- or 1,3-propylene, isobutylene, tetramethylene,pentamethylene, 2,2-dimethyltrimethylene, hexamethylene, anddecamethylene glycols, dihydroxy cyclohexane, cyclohexane dimethanol,hydroquinone-bis(beta-hydroxyethyl)ether resorcinol, hydroquinone,1,5-dihydroxy naphthalene, etc. Especially preferred are aliphatic diolscontaining 2-8 carbon atoms. Bis-phenols, such as bis(p-hydroxy)diphenyl, bis(p-hydroxyphenyl)methane and bis(p-hydroxyphenyl)propanecan be used.

An especially preferred group of copolyesters are those based onterephthalic acid, butanediol-1,4, and poly(tetramethylene oxide)glycol;optionally, containing phthalic acid and/or isophthalic acid as neededto reduce the melting point of the copolyester to the desired level.

As previously indicated, it is desirable to employ segmentedcopolyesters in this invention which have melting points below about215°C. The general relationship between monomer mole fraction andpolymer melting point is discussed by Flory, Principles of PolymerChemistry, page 570, Cornell University Press, 1953. He has suggestedthat the copolymer melting point (T_(m)) depends upon homopolymersmelting point (T.sub. m °), homopolymer mole fraction (N_(A)),homopolymer heat of fusion (ΔHμ) and the gas constant (R) in thefollowing way:

    1/T.sub.m -1/T.sub.m °=-(R/ΔHμ)1.sub.n N.sub.A

this equation is roughly valid for the class of copolyesters employed inthe blends of this invention. For copolyesters in which the major shortchain ester units are 1,4-butylene terephthalate units, T_(m) °≅234° C.and ΔHμ≅12.1 cal./g. To prepare copolyesters having melting points belowabout 215° C., it can be calculated that the mole fraction of1,4-butylene terephthalate units must be less than about 0.90. Thecalculated value is supported by the observed melting points of a numberof copolyesters based on 1,4-butylene terephthalate units. In a similarmanner, it has been found that copolyesters based on ethyleneterephthalate units should have a mole fraction of ethyleneterephthalate units not greater than about 0.85 to obtain copolyestersmelting below about 215° C.

The vinyl chloride polymers useful in this invention includehomopolymers and copolymers having a tensile modulus of at least about50,000 p.s.i. in the absence of agents such as flexibilizers orplasticizers. Tensile modulus is measured by ASTM D-638.

The copolymers which are useful include those containing up to about 30%by weight of units from interpolymerizable comonomers such as vinylacetate, vinyl stearate, vinylidene chloride, acrylonitrile, acrylateand methacrylate esters, dibutyl formate, and diethyl maleates.

Vinyl chloride polymers which are preferred for use in the presentinvention include vinyl chloride homopolymers and copolymers with vinylacetate and vinylidene chloride.

The blends of the present invention contain about 5-95% by weight of thecopolyester based on the total weight of the copolyester and vinylchloride polymer (excluding the weight of conventional additives,plasticizers and processing aids which may, of course, be employed withthe blends of the present invention). Blends of rigid vinyl chloridepolymers containing 5-25% copolyester are preferred for improving theimpact resistance and processing characteristics of rigid vinyls. Blendscontaining about 10-50% of copolyester are preferred for improving theproperties of plasticized vinyl chloride polymers. Such blends exhibitimproved abrasion resistance and load bearing characteristics and areuseful as heel lifts. Blends of 30 to 60 copolyester with unplasticizedvinyl chloride polymer resins wherein the copolyester functions as aplasticizer for the vinyl chloride polymer are particularly useful forupholstery, interior automotive applications, food packaging film, wallcovering, flooring, wire and cable coatings and the like. These blendshave good low temperature flexibility and are useful at elevatedtemperatures. The copolyester is permanent in these blends and resistsextraction, migration and aging. Blends containing about 60 to 90%copolyester are preferred for stiffening and improving thescuff-resistance and in some instances the tear strength of thecopolyesters while maintaining useful abrasion resistance. The blendsrich in copolyester are economical for use in shoe soling, molded tireswire coatings and coated fabrics.

For best results, in preparing the blends of this invention, thecomponents must be thoroughly and uniformly blended, otherwise localizedacreas will differ in properties. The compositions may be prepared byheating the components to a temperature sufficient to soften them andagitating until a uniform blend is formed. The temperature required tosoften or melt components depends on the particular copolyester andvinyl chloride polymer, but generally will be in the range of 150-215°C. Generally, it is preferred to use the lowest temperature which willpermit the mixing means available to be effective. If desired, solventsor plasticizers can be used to assist in mixing the copolyester with thevinyl chloride polymer at lower temperatures or to lower the mixingtemperature of copolyesters melting above about 215° C. Suitable mixingdevices include heated rubber mills, internal mixers (Banbury mixer) andtwin barrel extruders, or single screw extruders fitted with mixingattached to the screw. A particularly convenient procedure for preparingthe composition consists of dry blending a fine powder of the vinylchloride polymer with a fine powder of the copolyester and incorporatingthe vinyl chloride polymer into the copolyester in the barrel of anextruder or injection molding machine at the time the copolyester isbeing used to prepare extruded or molded goods. The vinyl chloridepolymer may also be conveniently added to the molten copolyesterimmediately following completion of the poly-condensation step incopolyester preparation. Blends can also be prepared by mixing vinyllatexes or powder dispersions with dispersions of copolyester. Suchmixtures can be employed in processes normally used for vinyl latices ordispersions. To obtain the maximum improvement in properties, fluxing ofthe mixture during processing is usually required.

Extrusion of such blends as described herein also reveals advantagesover the use of polymeric plasticizers such as thermoplastic urethanes.Firstly, the excellent melt stability of the segmented copolyesterspermits the use of a broader range of extrusion temperatures. Second,the extruded blend has little tendency to stick to highly polishedchrome-plated sheeting and calender rolls. (Thermoplastic urethanes areknown to stick badly to highly polished surfaces.) Thirdly, at thehigher levels of segmented copolyester (ca. 50-95%), the excellent meltstability and low melt viscosity permits the use of extrusion screws ofhigher compression ratio, permitting higher screw speeds and outputrates without an undesirable increase in melt temperature.

In addition to these processing advantages, property advantages such asimproved abrasion resistance, impact strength and low temperatureproperties are provided by the present blends as previously indicated.

The blends of this invention to be processed by substantially allprocedures which have been used for thermoplastics in general and, inmany instances, they offer significant processing advantage overcompetitive thermoplastic materials. The blends can be injection,compression, transfer and blow molded to form elastic molded articles,(such as tires), which may include inserts, if desired, meeting closetolerances. They can be readily extruded to produce films (blown orunblown), tubing, other forms having complicated cross sections, andcross-head extruded for hose, wire, cable and other substrate covers.They can be readily calendered to produce films and sheeting or toproduce calender-coat woven and nonwoven fabrics and other substances.

In finely divided form, the blends of this invention offer advantagesfor procedures employing powdered thermoplastics. In addition, they canbe used in crumb form. The flow characteristics of these blendsfacilitate fusion bonding procedures such as rotational molding (eitherone or two axis methods), slush molding, and centrifugal molding as wellas powder coating techniques such as fluidized bed, electrostatic spray,flame spray, flock coating, powder flow coating, cloud chamber and heatfused coating (for flexible substrates). Plastisols made from mixedvinyl-copolyester powder dispersions are useful for surface coatings,coated fabrics and foams.

The characteristics of these blends offer advantages for use in certaincoating and adhesive procedures such as dip, transfer, roller and knifecoating and hot melt adhesives. These same advantages are useful invarious combining and laminating operations such as hot roll, web andflame laminating as well as other thermoplastic heat sealing processes.

All parts, proportions and percentages disclosed herein are by weightunless otherwise indicated. The following examples further illustratethe invention.

Examples

Copolyester A is prepared by ester interchange of 4.53 moles of dimethylterephthalate hereinafter (DMT), 1.27 moles of dimethyl isophthalatehereinafter (DMI), 1.0 mole of polytetramethyleneether glycolhereinafter (PTMEG-980) (having a number average molecular weight about980) and excess 1,4-butanediol in the presence of a tetrabutyltitanate/magnesium acetate catalyst and a stabilizer[sym-di-beta-naphthyl-phenylene diamine or1,3,5-trimethyl-2,4,6-tri(3,5-di-tert-butyl-4-hydroxybenzyl)benzene].Ester interchange is conducted at atmospheric pressure up to a finaltemperature of 220° C. The ester interchange is followed bypolycondensation at 250° C. at about one torr for about 90 minutes. Athigher pressures a product having a lower inherent viscosity will beproduced but a higher rate of production will be obtained. Convenientlypressures of less than about 5 torr are employed. The resulting polymerhas an inherent viscosity of about 1.45-1.55.

Copolyester B is prepared by ester interchange of 3.5 moles of DMT, 1mole PTMEG-980 and excess 1,4-butanediol using the ester interchange andpolycondensation conditions and catalyst and stabilizer described forthe preparation of Copolyester A. Copolyester B has an inherentviscosity of about 1.5.

Copolyester C is prepared by ester interchange of 7.85 moles of DMT, 1mole PTMEG-980 and excess 1,4-butanediol using the ester interchange andpolycondensation conditions and catalyst described for the preparationof Copolyester A. Copolyester C has an inherent viscosity of about 1.45.

Inherent viscosities of the copolyesters described hereinbefore aremeasured at 30° C. at a concentration of 0.5 g./dcl. in a mixed solventof 60 parts liquid phenol (90% phenol; 10% water) and 40 parts of1,1,2-trichloroethane.

The following ASTM methods are employed in determining the properties ofthe polymers prepared in the examples which follow.

    ______________________________________                                        Modulus at 100% elongation, M.sub.100                                                                   D412                                                Modulus at 300% elongation, M.sub.300                                                                   D412                                                Tensile at break, T.sub.B D412                                                Elongation at break, percent                                                                            D412                                                Tear strength             D470                                                Hardness, Shore D         D1484                                               NBS Abrasion Index        D1630                                               Izod Import, notched      D256                                                ______________________________________                                    

EXAMPLE 1

Four polymer blends are prepared having the composition and propertiesset forth in Table I. For comparison, properties of the polymerscontained in the blends are included in the table. Blends containingCopolyester A are prepared by milling on a heated rubber mill for 10minutes at about 165° C. Blends containing Copolyester C are prepared inthe same manner with the mill at 185° C. Slabs (0.075" thickness) fordetermining physical properties were prepared by compression molding attemperatures approximating those required for milling.

                                      TABLE I                                     __________________________________________________________________________    Polymer blend or control                                                                       1-A  1-B  1-C  1-D  1-E  1-F  1-G                            __________________________________________________________________________    Component:                                                                     Vinyl chloride homopolymer.sup.1                                                                   67   50   100  67   50                                   Copolyester:                                                                   A              100  33   50                                                   C                                  33   50   100                            Properties:                                                                    Tensile strength, p.s.i                                                                       5,900                                                                              5,110                                                                              5,165                                                                              8,200                                                                              5,400                                                                              5,075                                                                              6,275                           Elongation at break, percent                                                                  805  290  370  35   250  335  730                             Modulus, 100%, p.s.i                                                                          925  2,600                                                                              1,755     3,080                                                                              2,315                                                                              2,250                          NBS abrasion index                                                                             800  522  410  275  1,275                                                                              1,275                                                                              3,540                          Hardness, Shore D                                                                              40   72   57   83   73   70   55                             __________________________________________________________________________     .sup.1 The vinyl chloride homopolymer is a rigid polyvinyl chloride           compounded with lubricants, stabilizers and pigments. It has a specific       gravity of 1.40 and a tensile modulus of 300,000 p.s.i. The material is       sold as Geon 82662 by F. B. Goodrich Chemical Company.                   

Addition of the copolyesters to the vinyl chloride homopolymer conferelastomeric character to the vinyl chloride homopolymer as indicated bylarge increases in elongation at break. At the same time, the abrasionresistance of the vinyl is increased markedly.

EXAMPLE 2

Ten parts of Copolyester A is blended with 100 parts of a rigid vinylchloride homopolymer (specific gravity 1.4; inherent viscosity by ASTMD-1243-60, Method A, 1.11, tensile modulus 300,000 p.s.i.) and 3 partsof dibutyl tin dilauryl mercaptide stabilizer by mixing for 10 minutesat about 165° C. on a rubber mill. The blend has a notched Izod impact,notched of 1.9 lbs./in. compared to 0.4 lb./in. for the straight rigidvinyl chloride homopolymer.

When the rigid vinyl chloride homopolymer is replaced by a vinylchloride (86%)/vinyl acetate (14%) copolymer having a tensile modulus of130,000 p.s.i. The Izod impact, notched, is 2.6 lbs./in. compared to avalue of 0.7 lb./in. for the straight copolymer.

The Izod impact strength of these blends at 140° F. is at least twice asgreat as the strength of the corresponding straight vinyl chloridepolymers. The brittle point of the blends is also lower than that of thestraight vinyl chloride polymers. The Shore D hardness of these blendsis substantially the same as the hardness of the unblended vinylchloride polymers.

EXAMPLE 3

A blend of 8 parts of the vinyl chloride homopolymer used in Example 1,4 parts of Copolyester A and 3 parts of dioctyl phthalate is prepared bymilling at 155-165° C. The NBS Abrasion Index of this blend is 960. Theblend contains 20% plasticizer. A blend of 4 parts of the vinyl chloridehomopolymer and 1 part of dioctyl phthalate has an NBS Abrasion Index ofonly 515.

EXAMPLE 4

A blend of 10 parts of a vinyl chloride (86%)/vinyl acetate (14%)copolymer having a specific gravity of 1.36 and a tensile modulus of150,000 p.s.i., 100 parts of Copolyester B and 3 parts of a mixedtriaryl phosphite stabilizer (Wytax 312, sold by National Polychemicals,Inc. Wilmington, Mass.) is prepared by milling for 10 minutes at about165° C. on a rubber mill. The resulting blend is optically clear andtransparent. Copolyester B in the absence of the vinyl copolymer is socloudy as to be nearly opaque in the form of an 0.075 inch thick sheet.

The blend has the following physical properties:

    ______________________________________                                        Modulus, 100%, p.s.i.    1060                                                 Modulus, 300%, p.s.i.    1350                                                 Elongation at break, percent                                                                           800                                                  Tensile strength         2200                                                 Trouser tear, p.l.i.     145                                                  ______________________________________                                    

The scuff resistance of the blend is substantially better than that ofthe straight Copolyester B as indicated by the amount of materialremoved and the chatter marks formed when a knife edge is drawn oversheets of the blend and the control copolyester.

We claim:
 1. A uniform blend of about 5-95% by weight vinyl chloridepolymer having a tensile modulus of at least about 50,000 p.s.i. andabout 95-5% by weight of at least one .Iadd.elastomeric.Iaddend.thermoplastic segmented copolyester .[.polymer.]. containing(1) about 5-90 weight percent long chain ester units derived from atleast one long chain glycol having a molecular weight of about 600--6000and having a melting point of less than about 60°C. and acarbon-to-oxygen ratio of at least about 2 and at least one lowmolecular weight dicarboxylic acid having a molecular weight less thanabout 300 and (2) about 10-95 weight percent short chain ester unitsderived from at least one low molecular weight diol having a molecularweight of less than about 250 and at least one low molecular weightdicarboxylic acid having a molecular weight of less than about 300, saidlong chain ester units and short chain ester units randomly joinedhead-to-tail through ester linkages, said long chain ester units beingrepresented by the formula ##EQU4##and said short chain ester unitsbeing represented by the formula ##EQU5##where G is a divalent radicalremaining after the removal of terminal hydroxyl groups from said longchain glycol; R is a divalent radical remaining after removal ofcarboxyl groups from said dicarboxylic acid; and D is a divalent radicalremaining after removal of hydroxyl from said low molecular weight diol.[...]..Iadd.; said copolyester having an inherent viscosity of at least0.6..Iaddend.
 2. The blend of claim 1 wherein the copolyester has amelting point of less than about 215°C.
 3. The blend of claim 1 whereinthe copolyester has 30-65 weight long chain ester units.
 4. The blend ofclaim 1 wherein the long chain glycols are selected from the groupconsisting of poly(tetramethylene oxide)glycol, poly(1,2-propyleneoxide)glycol, poly(ethylene oxide)glycol and poly(1,2-propylene oxide)glycol capped with ethylene oxide units.
 5. The blends of claim 1wherein the low molecular weight dicarboxylic acids are aromaticdicarboxylic acids containing 8-16 carbon atoms.
 6. The blends of claim1 wherein the low molecular weight diols are aliphatic diols containing2-8 carbon atoms.
 7. The blends of claim 1 wherein the vinyl chloridepolymer is a vinyl chloride homopolymer or copolymer containing up toabout 30% by weight of units from vinyl acetate or vinylidene chloride.8. The blends of claim 1 containing 5-25% copolyester.
 9. The blends ofclaim 1 containing about 10-50% copolyester.
 10. The blends of claim 1containing 30-60% copolyester.
 11. The blends of claim 1 containingabout 60-90% copolyester.
 12. The blend of claim 1 wherein thecopolyester is prepared by ester interchange of about 4.5 moles dimethylterephthalate, 1.3 moles dimethyl isophthalate, 1 molepolytetramethylene glycol having a number average molecular weight ofabout 980, and excess 1,4-butanediol in the presence of a catalyst and astabilizer, and polycondensation of the reaction product at about 250°C.13. The blend of claim 1 wherein the copolyester is prepared by esterinterchange of about 3.5 moles dimethyl terephthalate, 1 molepolytetramethyleneether glycol having a number average molecular weightof about 980, and excess 1,4 butanediol in the presence of a catalystand a stabilizer.Iadd., .Iaddend.and polycondensation of the resultingreaction product at about 250°C.
 14. The blend of claim 1 wherein thecopolyester is prepared by ester interchange of about 7.9 moles dimethylterephthalate, about 1 mole polytetramethyleneether glycol having anumber average molecular weight of about 980, and excess 1,4-butanediolin the presence of a catalyst and a stabilizer.Iadd., .Iaddend.andpolycondensation of the resulting reaction product at about 250°C..Iadd.15. The blend of claim 1 wherein said copolyester has an inherentviscosity of 0.8-1.5. .Iaddend..Iadd.16. In a composition wherein athermoplastic vinyl chloride polymer is uniformly blended with anelastomeric thermoplastic segmented copolyester, the improvement whereinsaid copolyester contains1) 30 to 65% by weight of long-chain esterunits derived from at least one long-chain glycol having a molecularweight of 600 to 6000 and at least one dicarboxylic acid having amolecular weight of less than 300, and 2) 70 to 35% by weight ofshort-chain ester units derived from at least one diol having amolecular weight of less than 250 and at least one dicarboxylic acidhaving a molecular weight of less than 300, and has an inherentviscosity of at least 0.6. .Iaddend..Iadd.17. The composition of claim16 wherein the long-chain glycol is poly(tetramethylene oxide)glycol..Iaddend..Iadd.18. The composition of claim 16 wherein the vinylchloride polymer is polyvinyl chloride and the blend contains 30 to 60%by weight of copolyester. .Iaddend..Iadd.19. The composition of claim 16wherein said copolyester has an inherent viscosity of 0.8-1.5. .Iaddend.